Liquid scintillation counting and automated instruments known as liquid scintillation counters are widely utilized to analyze samples having radioactively labeled substances. Generally, a sample in solution is mixed with a liquid scintillator, commonly referred to as a cocktail, and light events produced from the sample and cocktail mixture are detected according to their energy and frequency. The light events are caused when particles, emitted from the radioactive isotope labeling a select substance of the sample in solution are received by a molecule of liquid scintillator. This produces a light emission having an energy characteristic of the radioactive particle received. Detecting the energy of the light events and number of light events in a particular energy range provides an assemblage of information known as a spectrum from which the select substance of the sample, that material which is radioactively labeled, can be quantitatively analyzed. Liquid scintillation counting and automated instruments to perform liquid scintillation counting have been widely discussed in a multitude of publications and patents.
Scintillation counting of liquid samples possesses some characteristic disadvantages due to the nature of the liquid solution which is utilized. One is a phenomenon known as quench. Quench commonly refers to an effect in the scintillation process of the chemical or optical nature which results in loss of light events or reduction in light emission energy. It is in part due to the chemical nature of the solution in which the sample and scintillator are mixed and in part due to the color of the liquid sample solution. The result is inefficiently in the ability of the liquid scintillation counter to accurately count the particle disintegrations of the isotopes identifying the investigated material in the sample, thus, interfering with sample analysis.
Another disadvantage is the use of a liquid in which the radioactive sample and scintillator material, i.e., the cocktail, are intermixed. Following analysis this liquid solution and the vial in which it is held must be disposed of. However, regulations relating to disposal of radioactive materials impact disposal and control of the method in which disposal may be accomplished. This is particularly rigorous for liquid radioactive materials. Generally, samples are of a sufficient volume that specialized disposal methods must be followed which is quite costly. In many cases a solid material having a radioactive nature is treated differently.